Expedition M201 Finds 300-Meter Threshold for Explosive Mid-Atlantic Volcanoes Near Iceland
Updated
Updated · Quanta Magazine · May 26
Expedition M201 Finds 300-Meter Threshold for Explosive Mid-Atlantic Volcanoes Near Iceland
1 articles · Updated · Quanta Magazine · May 26
Scientists aboard Expedition M201 identified flat-topped, steep-sided volcanoes on the Reykjanes Ridge and argue they were formed by explosive eruptions, not the quiet lava outpourings typical of mid-ocean ridges.
At about 300 meters depth, the team says water pressure eases enough for seawater touching lava to flash into steam, driving blasts that can build islands before erosion cuts them back.
Historical records show at least 14 eruptions on the northern Reykjanes Ridge in 1,000 years, including Surtsey, which rose from the sea in 1963 and reached 171 meters above sea level.
The volcanoes' flat tops sit around 40 meters below sea level, matching the reach of North Atlantic storm-wave erosion, though one Icelandic geophysicist says more rock samples and direct imagery are needed to rule out an ice-age origin.
The finding suggests other shallow ridge segments—from the Azores to the Galápagos and Red Sea—could also produce short-lived islands, while renewed unrest around Iceland's Reykjanes system raises the odds of another offshore eruption.
As Iceland's glaciers melt, are they unleashing a new era of explosive volcanic eruptions?
The 'phantom islands' of maritime lore are real. When will the next volcanic island burst from the sea near Iceland?
Explosive volcanoes were found where quiet lava flows were expected. What does this mean for coastal hazard assessments globally?
Shallow Explosive Eruptions at the Mid-Atlantic Ridge: The 300-Meter Divide and Its Global Impacts
Overview
Expedition M201 near Iceland made a groundbreaking discovery that changes our understanding of volcanic eruptions along the Mid-Atlantic Ridge. Traditionally, the deep ocean’s immense pressure, found at depths of at least 2,500 meters, was thought to suppress explosive volcanism by preventing volcanic gases from expanding, resulting in quiet lava flows. However, the expedition revealed a critical boundary at about 300 meters below the sea surface, where this pressure is no longer enough to contain volcanic gases. This allows explosive eruptions to occur at much shallower depths than previously believed, fundamentally reshaping scientific views on submarine volcanism.